A normal helicopter departure requires the pilot to lower the nose of the aircraft slightly and to increase collective pitch to initiate forward flight and begin to climb. During the departure/climb phase of the flight, any problems, such as a loss of power, would be countered by raising the nose to initiate a flare to slow the helicopter for landing. In this occurrence, the pilot accelerated to about 40knots through translation in a level or slightly nose-down attitude, flying in a straight line for about 14seconds until impact. Engine and rotor sounds were normal, and wreckage examination did not reveal mechanical or control anomalies that would have prevented the helicopter from accelerating and climbing. The pilot had lifted off facing away from the sun and then had turned to face directly into the sun as he began forward flight. A more common departure procedure in a single-engine helicopter would be to turn 90degrees to the left or right, to accelerate and climb along the riverbank before turning out over the water. This would decrease the risk of having to ditch in the fast-flowing river in case of an engine or power train failure. The sun was at a low angle above his horizon and the bright sunlight was compounded by its strong reflection off the water. The resulting glare on and through the windscreen would have obscured the pilot's forward vision before his eyes could react to the sudden brightness, especially because he was not wearing sunglasses. The bright light would also have obscured the instrument panel in shadow, depriving the pilot of backup instrument information. During this period, the helicopter would have been accelerating. Somatogravic illusion would likely have caused the pilot to sense that the aircraft was climbing at about an 8.5-degree angle when, in fact, the aircraft was descending slightly until impact.Analysis A normal helicopter departure requires the pilot to lower the nose of the aircraft slightly and to increase collective pitch to initiate forward flight and begin to climb. During the departure/climb phase of the flight, any problems, such as a loss of power, would be countered by raising the nose to initiate a flare to slow the helicopter for landing. In this occurrence, the pilot accelerated to about 40knots through translation in a level or slightly nose-down attitude, flying in a straight line for about 14seconds until impact. Engine and rotor sounds were normal, and wreckage examination did not reveal mechanical or control anomalies that would have prevented the helicopter from accelerating and climbing. The pilot had lifted off facing away from the sun and then had turned to face directly into the sun as he began forward flight. A more common departure procedure in a single-engine helicopter would be to turn 90degrees to the left or right, to accelerate and climb along the riverbank before turning out over the water. This would decrease the risk of having to ditch in the fast-flowing river in case of an engine or power train failure. The sun was at a low angle above his horizon and the bright sunlight was compounded by its strong reflection off the water. The resulting glare on and through the windscreen would have obscured the pilot's forward vision before his eyes could react to the sudden brightness, especially because he was not wearing sunglasses. The bright light would also have obscured the instrument panel in shadow, depriving the pilot of backup instrument information. During this period, the helicopter would have been accelerating. Somatogravic illusion would likely have caused the pilot to sense that the aircraft was climbing at about an 8.5-degree angle when, in fact, the aircraft was descending slightly until impact. Findings as to Causes and Contributing Factors The pilot's forward vision was obscured by the bright sunlight and glare from the surface of the river. The pilot most likely lost visual reference with terrain and descended into the surface of the river. It is likely that the pilot did not realize that the helicopter was descending instead of climbing due to somatogravic illusion. Finding as to Risk Departing over water, instead of accelerating and climbing along the shoreline, increases the risk of losing visual references and the risk of ditching into water in the event of a power train failure.